Human milk contains a diverse and abundant set of neutral and acidic oligosaccharides. More than 130 different complex oligosaccharides have been identified in human milk, and their structural diversity and abundance is unique to humans. Although these molecules may not be utilized directly by infants for nutrition, they nevertheless serve critical roles in the establishment of a healthy gut microbiome, in the prevention of disease, and in immune function. Prior to the invention described herein, the ability to produce human milk oligosaccharides (HMOS) inexpensively was problematic. For example, their production through chemical synthesis was limited by stereo-specificity issues, precursor availability, product impurities, and high overall cost. As such, there is a pressing need for new strategies to inexpensively manufacture large quantities of HMOS.